NERVE PAIN

Affecting 6-10% of patients worldwide, neuropathic pain (NeP) represents an even greater burden than non-neuropathic chronic pain, significantly impacting on patients’ lives and with wider socio-economic consequences, warned pain specialists Dr Bethany Fitzmaurice and Dr Arasu Rayen in Treatments for neuropathic pain: up-to-date evidence and recommendations, published in BJA Education Volume 18.

Nerve pain is described as a process occurring after a primary lesion or disease of the somatosensory nervous system, by the International Association for the Study of Pain (IASP). Caused by a series of various pathological mechanisms, NeP is usually described based on the anatomic localisation. “This condition stems from an injury to either the peripheral or central nervous system (CNS) or to both and develops into a chronic disorder,” said pharmacotherapist Dr Hildegarde Berdine. She listed the following examples of NeP syndrome:

• Diabetic peripheral neuropathy (DPN)
• Phantom limb pain
• HIV sensory neuropathy
• Postherpetic neuralgia (PHN)
• Central poststroke pain
• Low back and neck pain with a neuropathic origin
• Complex regional pain syndrome
• Multiple sclerosis pain

“NeP is also associated with chemotherapy and direct traumatic injury to the nerves,” said Dr Berdine.

Classified as a type of chronic pain, NeP is characterised by the lowering of the pain threshold and excitation of the nerve pathways long after the initial injury has healed. The injury and malfunction to the nervous system become the source of pain and become a chronic disease.

MANAGEMENT OF NEP

“The approach to the management of nerve pain should focus on functional rehabilitation and aim to optimise quality of life in addition to pain relief," advised Dr Alexandra Monkhouse and Dr Tahir Ali John of Radcliffe Hospital. “Management options that should be considered for all neuropathic pain patients include behavioural therapy and psychological support, functional rehabilitation, and pharmacological therapy.

“Maintaining the patient’s function is a goal of equal importance to pain relief. Therapy aimed at optimising quality of life is crucial in patients who may experience various degrees of disability. Different conditions require different considerations, for example, physical therapy is integral in some neuropathic disorders such as complex regional pain syndrome and the use of prosthesis may be explored in amputees with stump pain or phantom limb pain. Non-pharmacological therapies, such as physiotherapy, massage, hypnosis, acupuncture, and Reiki should be considered and discussed.”

According to Dr Fitzmaurice and Dr Rayen, “The pharmacological treatment of NeP is challenging and inadequate for several reasons. These include diagnostic difficulties and insufficient knowledge about available treatment options,” they said. “Important and commonly prescribed medications may be unlicensed for these indications. Furthermore, available medications have limited effectiveness, adverse effects, and abuse potential.”

“Neuropathic pain tends to exhibit a relatively poor response to traditional analgesics,” Dr Katherine Galluzzi reported in Management of Neuropathic Pain (published in volume 105 of the Journal of the American Osteopathic Association). “Medications used to treat neuropathic pain include over-the-counter analgesics, anticonvulsants, tricyclic antidepressants (TCAs), topical anaesthetic agents, nonsteroidal anti-inflammatory drugs (NSAIDs), antiarrhythmics, and narcotic analgesics. This varied armamentarium reflects the heterogeneity of the patient group and the different pathophysiologic mechanisms postulated to produce neuropathic pain.

“Numerous treatment algorithms list trials of common analgesics such as ibuprofen or acetaminophen, topical treatment such as capsaicin cream or lidocaine patches, TCAs or other antidepressants (e.g. amitriptyline hydrochloride, desipramine hydrochloride), and anticonvulsants as first-line therapy for neuropathic pain. These medications may be used alone or in combination. The choice of medication should be directed toward the type of painful symptom described,” advised Dr Galluzzi.

MUSCULAR PAIN

Muscle pain or myalgia can be described as cramping and aching pain that originates in any muscle of the body, explained Professor Natalie Schellack et al. (The management of muscle pain published in volume 4 of SA Pharmaceutical Journal). “The pain can be in one targeted area or across many muscles, usually as a result of overexertion or overuse of these muscles.

“Myalgia may also occur without primary trauma and this is frequently associated with a viral infection. The severity of pain can range from mild to severe, depending on the cause,” said Prof Schellack. The pain can be acute or chronic, focal, or diffuse, in musculoskeletal or associated neural tissues. According to the International Association for the Study of Pain, symptoms include:

• Local symptoms of widespread and persistent pain
• Tenderness
• Peripheral nerve irritation
• Weakness
• Limited motion and stiffness

“Muscle pain can be caused by stress, tension, or physical activity,” said Prof Schellack. “Some medical conditions known to cause muscle pain include infections, hyper- or hypothyroidism, hypokalaemia, autoimmune conditions such as lupus, and side-effects of certain medications (e.g. statins).

MANAGEMENT OF MUSCLE PAIN

In Pain Management in Special Circumstances, authors Ahmed El Geziry et al. explained that the goals of non-pharmacological interventions are to decrease fear, distress, and anxiety, and to reduce pain and provide patients with a sense of control. “When deciding the most effective non-pharmacological technique, take into consideration the patient’s age, developmental level, medical history and prior experiences, current degree of pain, and/or anticipated pain. The advantage of non-pharmacological treatments is that they are relatively inexpensive and safe,” the authors said.

Fortunately, when non-pharmacological interventions aren’t enough, there are various classes of medicines that may be used in the management of muscle pain and injury. The two most common classes include narcotic analgesics and non-narcotic analgesics. “These agents have different mechanisms of action and will therefore have different side effects which should be taken into consideration when dispensing these agents to patients,” said Prof Schellack. Relevant analgesics can be taken orally (tablet or syrup), or topically (gel, cream, or patch). The benefit of topical application is that it provides localised pain relief.

• Non-narcotic analgesics: There are several non-narcotic analgesic agents available on the market for the management of pain. These medicines include paracetamol and NSAIDs like ibuprofen and diclofenac. Used to treat mild to moderate pain, when used in combination with a narcotic analgesic, these medicines can be used to manage severe pain.
• Narcotic analgesics: The third step in the pain treatment ladder, these provide analgesia for moderate to severe pain for the vast majority of patients and with a wide margin of safety Prof Schellack said. “This group includes codeine, morphine, oxycodone, methadone, fentanyl, and pethidine. Opioids can be divided into weak and strong opioids. Weak opioids are used alone or in combination with other analgesics, in the management of moderate pain. Strong opioids are usually reserved for severe pain.”

ADJUVANTS: “Adjuvant therapy is sometimes necessary to manage the side effects of pain medication, provide symptom relief, treat anxiety, and manage related or underlying conditions,” Prof Schellack explained. “This is because patients with chronic pain are more likely to report anxiety, depression, neuropathic pain, and significant activity limitations. Examples of adjuvant medicines include corticosteroids, anxiolytics, antidepressants, hypnotics, and anticonvulsants/antiepileptic agents.”